package org.bouncycastle.asn1;

import java.io.IOException;

/**
 * DER TaggedObject - in ASN.1 notation this is any object preceded by a [n]
 * where n is some number - these are assumed to follow the construction rules
 * (as with sequences).
 */
public class DERTaggedObject extends ASN1TaggedObject {
    private static final byte[] ZERO_BYTES = new byte[0];

    /**
     * @param tagNo
     *            the tag number for this object.
     * @param obj
     *            the tagged object.
     */
    public DERTaggedObject(int tagNo, DEREncodable obj) {
        super(tagNo, obj);
    }

    /**
     * @param explicit
     *            true if an explicitly tagged object.
     * @param tagNo
     *            the tag number for this object.
     * @param obj
     *            the tagged object.
     */
    public DERTaggedObject(boolean explicit, int tagNo, DEREncodable obj) {
        super(explicit, tagNo, obj);
    }

    /**
     * create an implicitly tagged object that contains a zero length sequence.
     */
    public DERTaggedObject(int tagNo) {
        super(false, tagNo, new DERSequence());
    }

    void encode(DEROutputStream out) throws IOException {
        if (!empty) {
            byte[] bytes = obj.getDERObject().getEncoded(DER);

            if (explicit) {
                out.writeEncoded(CONSTRUCTED | TAGGED, tagNo, bytes);
            } else {
                //
                // need to mark constructed types...
                //
                int flags;
                if ((bytes[0] & CONSTRUCTED) != 0) {
                    flags = CONSTRUCTED | TAGGED;
                } else {
                    flags = TAGGED;
                }

                out.writeTag(flags, tagNo);
                out.write(bytes, 1, bytes.length - 1);
            }
        } else {
            out.writeEncoded(CONSTRUCTED | TAGGED, tagNo, ZERO_BYTES);
        }
    }
}
